Check if an event overlaps with other events. https://pl.kotl.in/3G0a6x1fz

event_overlap_checker_algorithm.kt

private val appointmentEventList = mutableListOf<AppointmentEvent>()

/**
 * Note: Time should be 24 hours.
 **/
fun main() {

    appointmentEventList.add(AppointmentEvent(230, 300)) // 02:30 - 03:00
    appointmentEventList.add(AppointmentEvent(600, 700)) // 06:00 - 07:00
    appointmentEventList.add(AppointmentEvent(700, 800)) // 07:00 - 08:00
    appointmentEventList.add(AppointmentEvent(1000, 1030)) // 10:00 - 10:30
    appointmentEventList.add(AppointmentEvent(1100, 1200)) // 11:00 - 12:00
    

    println("AppointmentTime(3:00, 4:00): ${isValidTime(AppointmentEvent(300, 400))}")
    println("AppointmentTime(4:00, 5:00): ${isValidTime(AppointmentEvent(400, 500))}")
    println("AppointmentTime(5:00, 6:00): ${isValidTime(AppointmentEvent(500, 600))}")
    println("AppointmentTime(8:00, 10:00): ${isValidTime(AppointmentEvent(800, 1000))}")
    println("AppointmentTime(2:00, 4:00): ${isValidTime(AppointmentEvent(200, 400))}")
    println("AppointmentTime(5:00, 7:00): ${isValidTime(AppointmentEvent(500, 700))}")
    println("AppointmentTime(1:00, 2:00): ${isValidTime(AppointmentEvent(100, 200))}")
    println("AppointmentTime(11:00, 12:00): ${isValidTime(AppointmentEvent(1100, 1200))}")
    println("AppointmentTime(12:00, 13:00): ${isValidTime(AppointmentEvent(1200, 1300))}")
    
}

private fun isValidTime(targetEvent: AppointmentEvent): Boolean {
    // check if there is any event!
    if (appointmentEventList.isEmpty()) {
        return true
    }

    // Sort by end time
    appointmentEventList.sortBy {
        it.endTime
    }

    appointmentEventList.forEachIndexed { index, appointmentEvent ->

        // find the immediate next event of the target event
        if (appointmentEvent.startTime >= targetEvent.endTime) {
            // is it first?
            return if (index == 0) {
                true
            }
            // if not first
            else {
                // get previous one
                val previousAppointmentEvent = appointmentEventList[index - 1]

                // check end time
                previousAppointmentEvent.endTime <= targetEvent.startTime
            }
        }

    }

    // Check the end time of the last event
    if (appointmentEventList[appointmentEventList.size - 1].endTime <= targetEvent.startTime) {
        return true
    }

    return false
}

data class AppointmentEvent(
    val startTime: Int,
    val endTime: Int
)